The present invention relates to an image forming apparatus mounted, e.g. in a copying machine, a printer, etc., to which color electrophotography is applied.
There is known an image forming apparatus adopted a method of electrophotography, wherein a drum with a shaft is used as a photosensitive member. The image forming apparatus having the photosensitive drum is equipped with a drive apparatus for rotating the photosensitive drum.
This type of image forming apparatus is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-26903. The drive apparatus provided in the image forming apparatus uses a timing belt with teeth on its outer periphery as a torque transmission member. The timing belt is rotatably put around a plurality of support pulleys. A lower portion of the timing belt is engaged with a toothed pulley for driving. The drive apparatus is equipped with a tension applying mechanism for applying a tension at the lower portion of the timing belt.
The shaft of the photosensitive drum is attached to a toothed pulley. The photosensitive drum is located on the upper side of the timing belt and is detachably attached to the main body of the image forming apparatus. The toothed pulley of the photosensitive drum is engaged with an upper portion of the timing belt. When the driving toothed pulley is rotated, the timing belt is rotated. Further, the photosensitive drum is rotated via the toothed pulley for the drum.
This drive apparatus, however, has the following problem. The timing belt is provided with tension by the tension applying mechanism and is thus tightly stretched. As the photosensitive drum is set on the upper side of the timing belt, the toothed pulley for the drum comes in contact with the upper portion of the timing belt and pushes the timing belt inward (downward) into the area surrounded by the timing belt. When an outward (upward) force from the timing belt effect to the toothed pulley for the drum, the photosensitive drum may lift from the arranged position. It is thus necessary to fix the photosensitive drum to the main body of the image forming apparatus using mechanical means such as bolts, for preventing the photosensitive drum from lifting, against the force of the timing belt. This makes very difficult the operation of attaching the photosensitive drum to the main body of the image forming apparatus.
In addition, when the photosensitive drum is attached to the main body of the image forming apparatus, if the drum has been arranged at a position displaced from a preset arranged position, the teeth of the timing belt may be damaged by effecting a load to the timing belt and shifting the timing belt. In this case, a torque is not smoothly transmitted from the timing belt to the toothed pulley for the drum, and image formation is suffered a harmfle effect. It is thus necessary to fit the photosensitive drum precisely to a desired location. However, when the photosensitive drum is arranged on the upper side of the timing belt, it is difficult to fit the photosensitive drum precisely desired location and to exactly engage the photosensitive drum with the timing belt.
The purpose of the present invention is to provide a drive apparatus and an image forming apparatus having the drive apparatus, which is easy to operate attaching a photosensitive member to a main body of an image forming apparatus, which is possible to fit the photosensitive member precisely to a arranged location in the main body and to exactly engage the photosensitive member with a timing belt, and which can obtain a high-quality image.
According to the present invention, a photosensitive member is guided by a guide member so that the photosensitive member can easily and precisely be fit at an arranged position. When the photosensitive member has been moved to the arranged portion of the guide member, as the timing belt is pushed by a toothed pulley and wound around an outer peripheral surface of the toothed pulley, the timing belt is held at the wound position. Thus it can be avoid damaging the teeth of the timing belt, and lifting the photosensitive member from the arranged position, because the toothed pulley of the photosensitive member is exactly engaged with the timing belt.
A driving apparatus of the invention for supporting and rotating a photosensitive member with a shaft comprises: a guide member which guides the photosensitive member to an arranged position, the guide member including an attached portion which rotatably supports the photosensitive member at the arranged position, an insert/extract portion where the photosensitive member is inserted and extracted at an insert/extract position, and a guiding portion which guides the photosensitive member between the attached portion and the insert/extract portion in a direction perpendicular to an axial direction of the photosensitive member; a toothed pulley having teeth on an outer peripheral surface thereof and attached to the shaft of photosensitive member; a timing belt having teeth on an outer peripheral surface thereof; a plurality of support pulleys which support rotatably the timing belt as being wound around; a mechanism which rotates the timing belt; a tension applying mechanism which applies tension to the timing belt, the tension applying mechanism supporting the timing belt at a waiting position where the toothed pulley is in contact with the timing belt when the photosensitive member moves along the guiding portion of the guide member toward the attached portion, and the tension applying mechanism moving the timing belt to a winding position where the timing belt is wound around the outer peripheral surface of the toothed pulley centering at a contact portion been in contact with the toothed pulley when the photosensitive member has moved to the attached portion of the guide member; and a holding mechanism which maintains the timing belt in the winding position by the tension applying mechanism.
An image forming apparatus of the invention comprises an apparatus main body, a photosensitive member with a shaft, and a driving apparatus provided on the apparatus main body and supports and rotates the photosensitive member, wherein the driving apparatus comprises: a guide member which guides the photosensitive member to an arranged position, the guide member including an attached portion which rotatably supports the photosensitive member at the arranged position, an insert/extract portion where the photosensitive member is inserted and extracted at an insert/extract position, and a guiding portion which guides the shaft of the photosensitive member between the attached portion and the insert/extract portion in a direction perpendicular to an axial direction of the photosensitive member; a toothed pulley having teeth on an outer peripheral surface thereof and attached to the photosensitive member; a timing belt having teeth on an outer peripheral surface thereof; a plurality of support pulleys which supports rotatably the timing belt as being wound around; a mechanism which rotates the timing belt; a tension applying mechanism which applies tension to the timing belt, the tension applying mechanism supporting the timing belt at a waiting position where the toothed pulley is in contact with the timing belt when the photosensitive member moves along the guiding portion of the guide member toward the attached portion, and the tension applying mechanism moving the timing belt to a winding position where the timing belt is wound around the outer peripheral surface of the toothed pulley centering at a contact portion been in contact with the toothed pulley when the photosensitive member has moved to the guiding portion of the guide member; and a holding mechanism which maintains a state winding the timing belt around the outer peripheral surface of the toothed pulley by the tension applying mechanism.
A method of the invention for attaching a photosensitive member with a shaft to an apparatus main body of an image forming apparatus comprises: a step of preparing a guide member including an attached portion which rotatably supports the shaft of the photosensitive member at the attachment position, an insert/extract portion where is inserted and extracted the shaft of the photosensitive member at an insert/extract position, and a guiding portion which guides the photosensitive member between the attached portion and the insert/extract portion in a direction perpendicular to an axial direction of the photosensitive member; a step of rotatably supporting a timing belt having teeth on an outer peripheral surface thereof by means of a plurality of pulleys; a step of applying tension to the timing belt; a step of bringing a toothed pulley provided on the photosensitive member into contact with the timing belt when the photosensitive member is moved along the guiding portion of the guide member toward the attached portion; a step of moving the timing belt to a winding position where the timing belt is wound around an outer peripheral surface of the toothed pulley centering at a contact portion contacted with the toothed pulley when the photosensitive member has moved to the guiding portion of the guide member; and a step of holding the timing belt in the winding position.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.